Process of cleaning scale from bars



Nov. 1, 1932. E. LT. lcKEs 1,885,602

PROCESS OF CLEAING SCALE FROMKBARS Filed Sept. 10. 1930' 2 Sheets-Sheet V 1 wrmsssss NOV. 1, E. T [CKES lPROCESS OF CLEANING SCALE FROM BARS Filed Sept. 10. 1930 '2 vSheets-Sheet 2 INVENTOR;

Patented Nov. ,1, 1932 PATENT ori-lcs ELWOOD ICKES,'OF PITTSBURGH, PENNSYLVANIA l:PROCES F CLEANING SCALE FROMAIBABS Application n led September 10, 1930. Serial No. 480,943.

This invention pertains to the removal of scale from steel bars, and the like. Heretofore it has been recognized as desirable to remove scale, and otherwise to cleanse the surface, of steel products after various heat treatments that normally-occur in the course of manufacture. One ty e of such surface treatment is known as pickling. Up to the present time pickling in commercial practice has been accomplished principally by subjecting a steel object to the chemical action of acid, usually of sulfuric acid. The scale to be removed is an iron oxide. As this responds very slightly to direct action of the acid its removal principally is a mechanical-one with a chemical attack of the acid working considerable erosion and pitting of the body material. Not only has there thus been an expensive consumption of acid, but unsatisfactory results attend such practice. Further, the scale and fine particles of dust or other silicious matter remain very adherent and form a slimy coating so that final treatment has required not only careful washing of the article to remove all the acid but also various sorts of brushing or wiping to remove the coating. Moreover, the extended time required for acid pickling has contributed very considerably to the cost of this treatment.

Although acid pickling nevertheless has remained very general] the process in actual use, yinnovations have heen suggested; some of them directed to combining the chemical action of acid on the steel with various effects of the electric current actingthrough the solution in which the articles are immersed. -Such suggestions however, have proved to be defective for different reasons. It is to the cleansing of ferrous surfaces, such as of steel,

by electrochemical action combined effectively with other influences that this invention is directed with the result of making electrochemical pickling practicable under commercial operating conditions.

This invention best will be understood by reference to the accompanying drawings and description of a preferred illustrative embodiment thereof.

In the drawings, Fig. 1 represents a vertical section across an apparatus suitable for carrying out the process;

g1g. 2 is a plan view of such apparatus; an

Fig. 3 is a side elevation thereof. Referring to these drawings, it is apparent that the structure embodies a tank 1 of any design suitable to contain an acid solution, Along the tank, preferably along each side, extends an electrode 2, suitably connected to a source of positive direct current so as to act as an anode. Preferably the anode is of ferrous material, such as wrought iron, ingot iron, Toncan metal, or mild steel under 0.30 carbon. It is preferable further to employ anodes placed as shown along opposite sides of the cleaning tank and as plates extending practically the height of the solution. Provision is made to suspend the material to be cleaned and suitably to agitate it and tumble the individual units' upon themselves in the solution. The electrical connections are such that the material being treated becomes the cathode, and preferably this is accomplished .by suspendmg such material in 75 chains and causing the chains to become the cathode. As shown the stock to be pickled is designated as 3, suspended freely in chains 4. Suitable supports 5 are disposed along the tank fora plurality of chains, or other agitator. -In the embodiment shown such supports rise outside the tank with arms extending over the walls. Peferably an arm 6 contains an equalizing adjustment for a stationary end of the corresponding chain, while the opposed arm 7 supports a rotary shaft with a suitable number of drums 8 upon whichv the other end of the chain is adapted to wind. Oscillatory motion is imparted to this shaft and drum so thatA as the chain alternately winds and unwinds the loop is shortened and lengthened to provide requisite rolling agitation for the4 metal articles suspended therein. Suitable crank connections toa source of power such as a motor M provide an adequate rate of agitation.

Preferably also the tank is associated with means t elevate the temperature Yof the solution and to increase the violence of agitation of the electrolyte as it courses through theblOO metal articles. In the embodiment shown in the drawings this is accomplished by a steam line 9 along the middle of the tank near the bottom. With this mode of heating, orifices may be provided for the injection of steam into the solution. In this form also the bottom of the tank preferably inclines downwardly from the steam line toward -each side. Thus agitation of the solution through the units being cleaned is improved, as well as heating and cleaning. The purpose of the agitation of the solution is to cause a churning of the electrolyte through the metal articles'. Other means than the injection of steam would comprise the injection of heated air or would include electric heating units for example, so positioned' in the preferred arrangement as to su plement any turbulence or any natural circu ation due to convection currents. A

In operation, the tank is filled to above the material to be cleaned, withv an electrolyte,

preferably of sulfuric or Aof hydrochloric acid 1n 0.5 to 3.0% solution. The solution is adjusted to a suitablel lelevated temperature, preferably to 150 F. or even toboiling. With the current flowing, the articles as cathodes constantly are agitated and rolled over and over against each other; thus while being subjected to the requisite electrolytic action they are not only cleaned of any adhering film but all sides of all of the articles become successively exposed toward an anode for Vsuliicient duration of time to insure adequate surface treatment.

It is of considerable importance that under the practice of this invention the current be controlled and preferably limited to low values. The voltages may range from referred values of about'six volts up to va ues of approximately forty volts and the amperages rom preferred values of about two and a half amperes per square foot of cathode up to approximately forty amperes per square foot. Variations will depend on the character, composition and shape of the steel to be cleaned, the strength of the electrolyte, time of treatment, e l

With some grades of steel, for example such as the high-chromium, acid-resistant type, it is of added, benefit to reverse the direction of current for a short period of time at the end of the cleaning operation.

The advantages of this invention are manifested not4 only in the various economies effected and not only. in the improved' surfaces obtained, butvin the ready and satisfactory cleaningof complicated surfaces such as a plurality of 'steel rods, pipes, bars of irregular section, and the like. The range of objects is not limited to those of any one type, but the principles of this invention extend particularly to the varieties of steel bar products undergoing treatment commercially.

rods, and the like articles fo` Alternative embodiments of the principles of this invention will b e feasible, for the invention is not restricted to the specific features to which reference has been made in accordance with the patent statutes for the purpose of illustration. Such alternatives are intended to be within the scope of the appended claims except as limited lby the prior art to which this invention pertains.

What is claimed is:

1. A process of pickling a plurality of bars,A

rods, and the like articles formed of ferrous metal, comprising suspending the articles in a bath of mineral acid heated to an elevated temperature and containing from about 0.5 to 3.0 per cent of acid, and tumbling the articles upon themselves while passing a direct electric current from a ferrous metal anode through the bath to the articles as cathodes, the current density being from about 2.5 to 40 amperes per square foot of exposed cathode surface, and thereby removin surface scale from the articles and providing them with clean ferrousmetal surfaces.

2. A process of pickling a plurality of bars, ed of ferrous metal, comprising suspending the articles in a bath containing. from about 0.5 to 3.0 per cent of an acid of the group comprising sulfuric and hydrochloric acids, the bath being heated to about 150 to 200 F. and tumbling the articles u on themselves while passing a direct electric current from a ferrous metal anode through the bath to the articles as cathodes, the current? density being from about 2.5 to 40 amperes per square oot of exposed cathode surface, and thereby removin surface scale from the articles and provi ing them with clean ferrous metal surfaces.

3. A process of pickling a plurality of bars, rods, and the like articles formed of ferrous alloy containing chromium, comprising suspendin the articles in a bath containing from a out 0.5 to 3.0 per cent of mineral acid and heated to a tem rature of about 150 to 200 F. and tum ling the articles upon themselves while continuously passin a direct electric current from a ferrous meta anode throughthe bath to the articles as cathodes, the current density being from about 2.5 to 40 amperes per square foot of exposed cathode surface, and after pickling has been completed momentarily passing a direct currentin the opposite direction, and thereby removing surface scale from the articles and providing them with clean ferrous metal surfaces.

In testimony whereof I si myJname.

ELwoo T. IoKEs. 

